Internet users are being plagued by more spam e-mails but are less bothered by the onslaught of unsolicited pitches, according to a report released Wednesday.

The survey by the Pew Internet & American Life Project found that 37 percent of consumers said they are getting more spam in their personal e-mail accounts than in the past. However, only 18 percent called spam a big problem, down from a quarter of all respondents four years ago.

The findings reflect that consumers are increasingly fighting back against spam by using filters to keep their inboxes clear, a highly recommended but only partially effective tactic. Psychology may offer another explanation: Internet users may simply be getting used to the flood of unsolicited e-mails and now consider it normal.

"People are taking action -- they're putting up defenses or are finding ways themselves to shield their e-mail addresses," said Susannah Fox, associate director of the Pew Internet & American Life Project, a research organization in Washington. "Or maybe people may have grown used to it."

Whatever the case, the study shows that Internet users are largely undeterred by spam, contradicting speculation several years ago that e-mail was doomed because of pitches for Viagra, work-at-home offers and get-rich-quick schemes from Nigeria. The vast majority of Internet users, 91 percent, use e-mail, although just over half said that they are less trusting of what they read in their inboxes.

For years, Internet users have been desperate for a solution to spam, without much luck. A federal law, the Can-Spam Act of 2003, created rules for commercial e-mail and created penalties for those who violate the law, but it ultimately failed to reduce the volume of unwanted messages.

For example, Barracuda Networks, a Mountain View company that sells spam and virus filters, said spam volume quintupled over five months last year. Various studies show that 80 to 95 percent of all e-mail is now spam.

Simply sorting through in-boxes to find legitimate messages from friends, colleagues and clients eats up a lot of time. Virtually anyone who relies on e-mail to do his or her job knows the cost to productivity.

"Normally you may get 50 e-mails a day with a spam filter," said Dean Drako, chief executive of Barracuda Networks. "But without, you might get thousands, so you can't find your real e-mail."

Filtering spam is a constant struggle because of the changing tactics by those who send the messages. Many spammers are based outside the country and bounce their pitches between various computers to increase the likelihood that their e-mails elude junk mail folders.

For its study, Pew surveyed 2,200 adults, 1,405 of whom were e-mail users, with a margin for error of plus or minus three percentage points.

While fewer Internet users call spam a big problem, fewer also took the middle ground in describing spam as an annoyance. Just over half of the respondents did so, down from 57 percent four years ago.

In another sign of shifting attitudes, more e-mail users said spam is not at all a problem -- 28 percent versus 16 percent in 2003.

The reasons for the changes in thinking about spam are many. Pornographic messages, which elicited a particularly negative reaction from women, are down sharply (52 percent of respondents said they received at least one such e-mail compared with 71 percent three years ago) and more said they use spam filters (71 percent versus 65 percent two years ago).

Given the complaints about spam, the question remains whether it is even a profitable endeavor. The Pew survey didn't address the issue, other than to ask if respondents ordered a product from an unsolicited e-mail.